1. Field of the Invention
This invention relates of a method of determining the degree of aggregation of the .beta.A4 peptide (SEQ ID NO:1-4) and more particularly to detecting the protein by reacting the protein with a suitable binding reagent and measuring the amount of resultant unreacted binding reagent.
2. Discussion of the Prior Art
It is known that the brain of patients having Alzheimer's Disease contains aggregations or clumps of a small fragment of the beta-amyloid precursor protein which fragment is known as the amyloid beta-peptide or the .beta.A4 peptide. The 42-mer peptide sequence of the .beta.A4 peptide (SEQ ID NO:1-4) is Aspartate-Alanine-Glutamate-Phenylalanine-Arginine-Histidine-Aspartate-Ser ine-Glycine-Tyrosine-Glutamate-Valine-Histidine-Histidine-Glutamine-Lysine- Leucine-Valine-Phenylalnine-Phenylalanine-Alanine-Glutamate-Aspartate-Valin e-Glycine-Serine-Aspargine-Lysine-Glycine-Alanine-Isoleucine-Isoleucine-Gly cine-Leucine-Methionine-Valine-Glycine-Glycine-Valine-Valine-Isoleucine-Ala nine. (DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA) (SEQ ID:4).
For a general discussion on the .beta.A4 peptide (SEQ ID NO:1-4) and Alzheimer's Disease, reference is made to Dennis J. Selko, Scientific American, November 1991, 68-78, and Joseph T. Jarrett et al., Cell, Vol. 73, 1055-1058 (1993).
A potential treatment for combating the progress of Alzheimer's Disease is to use a drug comprising an active ingredient which prevents the aggregation or clumping of the .beta.A4 peptide. Accordingly, a screening test for identifying such active ingredient or effective chemical compound is needed.
There are various assays known in the art for detecting proteins per se. One such assay involves the use of Bradford dye, or as it is also known as Coomassie Brilliant Blue G250. In this regard, reference is made to J. James Sedmak et al., Analytical Biochemistry, 79, 544-552 (1977), which describes an assay for proteins but not for the A4 peptide whether in the aggregate or free state.
What is required and desired is an assay for the .beta.A4 peptide which distinguishes such protein in the aggregate state from when it is in the free or unaggregated state and reflects the effect of various compounds on such aggregate state. In this regard, H. LeVine, Protein Science, 2, 404-410 (1993) describes the detection of aggregated amyloid employing Thioflavin T.